What wrench or socket to use
 

Anybody have a recommendation on what wrench or socket to use on this "combination nut"?

I think that's a "triple square" nut. A quick google image search brings up lots of male drive sockets, but no female drive sockets. Might look at Snap On, Mac, Matco and see if the tool trucks carry something appropriate.

answered on bimmerfest. Hazet 12point ...36mm maybe? Most of the tool vans (Matco, SnapOn, Mac) should have one, or Pelican parts

Good practices = good results
 

The tool for this job is a good quality '12 point' socket. 1/2 inch drive will be adequate. Sears, and the usual auto parts stores will sell them. Your safety is at risk when you use poor quality tools.

However, removing this nut MUST be approached with the thought "you will have only a single chance to properly remove it". If the wrench slips and mars the flats on this nut, you will play hell getting it off.

All sockets are manufactured with a bit of taper or 'lead' (rhymes with bleed) machined into the opening of the socket. This is to aid the mechanic in placing the socket over the nut. In this case, the lead is not your friend, but is your foe.

The lead will allow only half of the available 'flat' of the nut to be against the faces inside the socket. This tends to force the socket to 'cam-out' and off of a shallow nut, damaging the nut, and injuring the mechanic. I strongly advise the mechanic to grind the end the socket to remove the lead, or better yet, have a friend with a lathe cut the socket face square.

An additional 'dodge' known to most mechanics is to rub a smear of valve grinding compound onto the flats of the nut OR inside the face of the socket. The grit in the valve grinding compound greatly increases the 'grip' of the socket reducing cam-out or slip.

Be very careful, the torque value to remove this fastener will be around 100 lbs/ft. A straight, steady pull is required and avoid jerking. The vehicle must be secure on jack stands and or blocks.

Below are two photos, one showing a typical 12 point socket and depth of the lead, and a package of valve grinding compound, both avalable at most auto part stores.

Best wishes,
Dick

PS: A shot of a known brand of Penetrating Oil, applied 30 minutes prior to removing the nut, is worth considering. Aero Kroil is my favorite, but Liquid Wrench and others are readily available.

Thanks rcasey, exactly the answer and advice I was looking for! I have a pretty good 30mm 12 point socket and I am all too familiar with the socket slipping .... have the stitches in the hand to prove it!

My additional challenge is that the ball joint "stud" will have to be held steady. This is done by holding it in place with an Allen wrench, and then use an "open", 12 point socket ... (BMW "special" tool).

Any idea where to get that type of a tool?

You'll need something similar to this. Search for Pass-Through socket.
...or just use an impact gun.
http://c745.r45.cf2.rackcdn.com/img/...n_passthru.jpg

Basora, like most ball joints, the joint is comprised of a 'ball & socket' attached to a 'self-locking' taper and a threaded end to pull the taper into a 'very tight seat'. You will not need a hex key for disassembly.

The hex-key socket is used during assembly to keep the taper from turning. Using a common box-end wrench on the nut, and a hex key in the end of the taper, the mechanic begins to pull the taper well into the mating hole in the control arm, and the friction in the self-locking taper will be sufficient that the hex key is no longer required. Final assembly simply replaces the box end wrench with a socket and torque wrench, following BMW's task #31 12 004. Please note, you will need to use a fresh nut upon reassembly.

Your biggest hurdle will be removing the ball joint after you remove the nut. The ball joint will be very tight in that control arm. VERY tight!

BMW shows using a screw style Ball Joint Separator. Please see screen shot photo below. To show the taper, a representative photo of a generic ball joint is shown as well.

best wishes,
Dick

Thanks again!

You said (recommend?) to use a new nut on assembly ... the parts guy at the BMW dealership said the same ...

Price for one "nut"? A whopping $17!!! With my discount it was still $14. I declined.

Of course I'll buy it once I am convinced that I must replace it, but I looked at the nut very carefully and could not find any design features that suggest that the nut can be compromised after use or otherwise rendered unusable after being installed once. Comments?

Also, I bought the whole arm ($200/ea!): so no need to separate the ball joint from the trust arm.

I have the screw style Ball Joint Separator.

That looks to me like a single use jam nut. Cut tapers on the end. It could be reused but shouldn't.

Do not ever re-use a nut like this- they are made for one use only. $14 is cheap insurance to avoid a ball joint separation on the road.

Hi Basora: I hope never to sound harsh with my response.

Lets take the easiest part of your recent post. I gather I was not clear e'nuff in my explanation about the taper and the ball joint. I am not suggesting you will be removing the ball end from the thrust arm you have shown in your photo.

Removing the old thrust arm will require you pulling the old taper from the control arm on the wheel spindle. Removing the nut will be the easy part.

As to the question "New nut or old". This is where I may seem to be harsh. It is not my intention. BMW's repair manual directs their dealerships all over the world to comply with the standards in their instruction manuals. This is for safety, reliability, and from great empirical evidence. In the task I quoted earlier, BMW directs the factory trained mechanics to replace the nut. Period. I simply quoted BMW when I told you you would need a new nut, as did the parts guy.

You have decided you want to replace the worn thrust arm yourself. This might be to save money, perhaps you like to work on your own car, or some combination of the two. You need to ask yourself a question. "If I were to hire BMW to do the job, and I later found that they failed to precisely follow the factory workshop and re-used a part that was specified as requiring replacement, would I be satisfied or not?"

How you answer that question may help you decide on how to proceed.

BMW has perhaps recognized that some components, like this self-locking nut, are a critical component, and should that component fail, loss of life may result. Nuts of the construction used in this case employ a self locking feature in the finger like tangs. Once used, the self locking effect is compromised.

So I ask you, "When working on your own vehicle, why should your standards be any less than those of a factory trained mechanic?"

Please carefully consider the small savings involved.

Be Safe,
Dick

Never too harsh and I don't mind at all. The above says it all: this type nut has self-locking features. Once use they are compromised. I completely understand now. Buying 2 new nuts tomorrow!

Thanks again.